Optical display device

ABSTRACT

There is provided an optical disc device comprising a step number calculation means ( 110 ) for calculating the number of steps of a motor ( 106 ) on the basis of the target number of tracks required for traverse seek; a differential number calculation means ( 112 ) for calculating the number of differential tracks over which an objective lens should be shifted, on the basis of the target number of tracks and the number of steps; and a tracking jump control means ( 113 ) for driving an actuator ( 104 ) at track intervals by applying a control signal generated on the basis of the number of differential tracks, to an actuator driving circuit ( 114 ). After advancing a traverse ( 105 ) by driving the motor by the number of steps calculated by the step number calculation means, tracking-jump is carried out over the differential tracks to shift an objective lens ( 103 ).

TECHNICAL FIELD

The present invention relates to an optical disc device and, moreparticularly, to an optical disc device that drives a traverse atintervals corresponding to a predetermined number of tracks, in thedirection of the radius of an optical disc, thereby accessing to atarget track.

BACKGROUND ART

In recent years, there has been developed optical disc devices forrecording or reproducing data in/from an optical disc having spiraltracks, such as a CD (Compact Disk), MD (Mini Disk), DVD (DigitalVersatile Disk), and the like. In these optical disc devices, anobjective lens is shifted in the direction of the radius of the opticaldisc to make an access to a target track.

For example, there has been proposed an optical disc device thatrealizes an accurate access to a target track by shifting an opticalpickup which movably holds an objective lens in the direction of theradius of an optical disc, over a predetermined number of tracks.Specifically, this optical disc device continuously reads addresses oftracks on the optical disc for a predetermined period of timeimmediately after a command for shifting is made, and corrects the countof the number of tracks during shifting by a counter according to theread addresses, thereby to realize an accurate access (for example,refer to Patent Document 1).

Patent Document 1

-   -   Japanese Published Patent Application No. Hei. 5-101412

Further, there has been proposed an optical disc device that performs anaccess to a target track by traverse seek. Hereinafter, a descriptionwill be given of the construction and operation of a conventionaloptical disc device that performs traverse seek, with reference to FIG.13.

A conventional optical disc device 600 includes a disc motor 102 forrotating an optical disc 101 on which data are recorded in tracks; anobjective lens 103 for irradiating the optical disc 101 with a laserbeam and receiving a reflected light beam; an actuator 104 for movingthe objective lens 103 in the direction of the radius of the opticaldisc 101; a traverse 105 for holding the objective lens 103 and.theactuator 104 movably in the direction of the radius of the optical disc101; and a motor 106 for driving the traverse 105 in the direction ofthe radius of the optical disc 101. Further, the optical disc device 600includes a tracking error signal generation circuit 107 for calculatingan error between the position of a track on the optical disc 101 and theposition of the objective lens 103 that is a laser beam irradiationposition, on the basis of the reflected light beam received by theobjective lens 103, thereby generating a tracking error signal as anerror signal; a tracking servo filter 108 for generating a trackingdrive output for making the objective lens 103 follow the track on theoptical disc 101 (hereinafter referred to as “tracking on”) on the basisof the tracking error signal outputted from the tracking error signalgeneration circuit 107; an actuator driving circuit 601 for driving theactuator 104 on the basis of the tracking drive output outputted by thetracking servo filter 108; a target number calculation means 109 forcalculating the number of tracks up to the target track (hereinafterreferred to as “target number of tracks”), on the basis of a targettrack address AD2 to which an access should be made, and an address of atrack where the objective lens 103 is positioned at starting of traverseseek (hereinafter referred to as “current track address AD1); a stepnumber calculation means 110 for calculating the number of steps forshifting the traverse 105 on the basis of the target number of tracks;and a motor driving circuit 111 for driving the motor 106 on the basisof the output of the step number calculation means 110.

FIG. 14 shows the positional relationships among the tracks on theoptical disc 101, the objective lens 103, and the traverse 105 duringtraverse seek.

During traverse seek, the motor 106 shifts the traverse 105 at apredetermined interval L1 or an interval equal to an integral multipleof the predetermined interval L1. The predetermined interval L1 is equalto a track interval D1 or an integral multiple of the track interval D1.Hereinafter, a distance corresponding to the predetermined interval L1or an integral multiple of the interval L1, which is traveled by thetraverse 105 being driven by the motor 106, is referred to as a step.

Next, a description will be given of a method of performing traverseseek by the conventional optical disc device 600 constituted asdescribed above.

FIG. 15 is a flowchart for explaining the method of performing traverseseek by the conventional optical disc device 600.

When traverse seek is started, the target number calculation means 109calculates the target number of tracks on the basis of the target trackaddress AD2 and the current track address AD1 where the objective lens103 is positioned at start of traverse seek. Then, the step numbercalculation means 110 calculates the amount of shift of the traverse 105for tracking on the target track, and converts the calculated amount ofshift into the number of steps of the motor 106. As shown in FIG. 14,when there is a distance equivalent to 43 tracks from the track at whichthe traverse seek is started to the target track, and the predeterminedinterval L1 by which the motor 106 shifts the traverse 105 by one stepis equivalent to 13 tracks, the number of steps calculated by the stepnumber calculation means 110 is 3 (step S91).

Next, the track-following operation is stopped (tracking off) (stepS92). Then, the motor driving circuit 111 drives the motor 106 by thenumber of steps calculated in step S91, thereby moving the traverse 105.As shown in FIG. 14, the traverse 105 is shifted by 3 steps on the basisof the number of steps calculated by the step number calculation means110 (step S93). Then, tracking-on is carried out again (step S94) toobtain the address (step S95).

When the obtained address is the target track address AD2, since theobjective lens 103 accesses the target track at this time, the traverseseek is ended (step S96). On the other hand, when it is not the targettrack address AD2, the objective lens 103 is brought closer to thetarget track by tracking jump, i.e., by shifting~the objective lens 103at track intervals by the actuator 104. In the example shown in FIG. 14,tracking jump is carried out over four tracks. At this time, the amountof lens shift immediately before the traverse seek due to thetrack-following operation is incorporated in traverse advancing andcompensated (step S97). Then, an address acquisition means (not shown)obtains the address of the track on which the objective lens 103 istracking on, thereby to complete the processing (step S98).

As described above, since the distance traveled by the traverse 105 byone step of the motor 106 is longer than the track interval D1, themotor 106 cannot drive the traverse 105 at the track interval D1.Therefore, when there is an error between the number of tracks to beachieved in traverse seek (target number of tracks) and the number oftracks over which the traverse 105 is actually shifted by the motor 106,tracking on the target track cannot be carried out by traverse seek.

When tracking on the target track fails, in order to realize an accurateaccess during traverse seek, tracking-on is carried out to obtain theaddress after advancing the traverse 105, and the number of tracks fromthe currently tracking-on track to the target track is calculated tomake an access again. This results in an increase in time required foraccessing the target track.

The present invention is made to solve the above-described problems andhas for its object to provide an optical disc device that reduces accesstime during traverse seek, and performs accurate access to the targettrack.

DISCLOSURE OF THE INVENTION

In order to solve the above-mentioned problems, an optical disc deviceaccording to claim 1 of the present invention comprises: an actuator formoving an objective lens that irradiates an optical disc with a laserbeam; a traverse for holding the objective lens and the actuator so thatthe objective lens and the actuator are mutually movable; a motor forperforming step driving to advance the traverse for every unit traveldistance; an actuator driving means for driving the actuator on thebasis of an error between the position of a track on the optical discand the position to which the objective lens applies the laser beam,thereby to make the objective lens follow the track on the optical disc;and a motor driving means for calculating the number of steps on thebasis of the number of tracks from the position of the objective lens upto a target track to be accessed, and driving the traverse by thecalculated number of steps; wherein the actuator driving meanscalculates the number of tracks from the position of the objective lensup to the target track to be accessed, and driving the actuator so as toshift the objective lens up to the target track on the basis of thecalculated number of tracks.

According to claim 2 of the present invention, the optical disc deviceaccording to claim 1 further comprises a target number calculation meansfor calculating the number of tracks up to the target track on the basisof a current address where the objective lens is currently positioned,and the target track address; the motor drives the traverse by apredetermined number of tracks as one step of unit travel distance; themotor driving circuit calculates the number of steps for driving thetraverse by the motor, on the basis of the target number of tracks thatis calculated by the target number calculation means, and the unittravel distance of the motor, and drives the traverse by the calculatednumber of steps; and the actuator driving means calculates the number oftracks from the position of the objective lens up to the target trackafter advancing the traverse by the motor, and drives the actuator attrack intervals so as to shift the objective lens by the calculatednumber of tracks.

According to claim 3 of the present invention, the optical disc deviceas defined in claim 1 further comprises a target number calculationmeans for calculating the number of tracks up to the target track on thebasis of a current address where the objective lens is currentlypositioned, and the target track address; the motor drives the traverseby a predetermined number of tracks as one step of unit travel distance;the motor driving circuit calculates the number of steps for driving thetraverse by the motor, on the basis of the target number of tracks thatis calculated by the target number calculation means, and the unittravel distance of the motor, and drives the traverse by the calculatednumber of steps; and the actuator driving means calculates the distancefrom the position of the objective lens after advancing the traverse bythe motor, up to the target track, and drives the actuator so as toshift the objective lens by the calculated distance.

According to claim 4 of the present invention, an optical disc devicecomprises: an actuator for moving an objective lens that irradiates anoptical disc with a laser beam; a traverse for holding the objectivelens and the actuator so that the objective lens and the actuator aremutually movable; a motor for performing step driving to advance thetraverse for every unit travel distance; an actuator driving means forgenerating a first tracking drive signal on the basis of an errorbetween the position of a track on the optical disc and the position towhich the objective lens applies the laser beam, and applying the firsttracking drive signal to the actuator to make the objective lens followthe track on the optical disc; a ratio calculation means for shiftingthe objective lens at track intervals over a predetermined number oftracks to obtain the amount of shift of the objective lens and the firsttracking drive signal at this time, and calculating the ratio of theamount of shift of the objective lens to the first tracking drivesignal; a target number calculation means for calculating the number oftracks up to the target track on the basis of a current address wherethe objective lens is currently positioned, and a target track addressto be accessed; and a motor driving means for calculating the number ofsteps for advancing the traverse by the motor, on the basis of thetarget number of tracks calculated by the target number calculationmeans and the unit travel distance of the motor, and driving the motorby the calculated number of steps; wherein the actuator driving meanscalculates the distance from the position of the objective lens afteradvancing the traverse by the motor, up to the target track, generates asecond tracking drive signal on the basis of the calculated distance andthe ratio, and drives the actuator to shift the objective lens up to thetarget track.

According to claim 5 of the present invention, in the optical discdevice according to claim 4, the ratio calculation means calculates theratio of the amount of shift of the objective lens, which amount ofshift is obtained when rotating the optical disc with the traverse beingfixed and the objective lens following the track, to the first trackingdrive signal.

According to claim 6 of the present invention, in the optical discdevice according to claim 4, the ratio calculation means calculates theratio of the amount of shift of the objective lens, which amount ofshift is obtained when advancing the traverse by a predetermineddistance with the objective lens being held, to the first tracking drivesignal.

As described above, the optical disc device according to claim 1 of thepresent invention comprises: an actuator for moving an objective lensthat irradiates an optical disc with a laser beam; a traverse forholding the objective lens and the actuator so that the objective lensand the actuator are mutually movable; a motor for performing stepdriving to advance the traverse for every unit travel distance; anactuator driving means for driving the actuator on the basis of an errorbetween the position of a track on the optical disc and the position towhich the objective lens applies the laser beam, thereby to make theobjective lens follow the track on the optical disc; and a motor drivingmeans for calculating the number of steps on the basis of the number oftracks from the position of the objective lens up to a target track tobe accessed, and driving the traverse by the calculated number of steps;wherein the actuator driving means calculates the number of tracks fromthe position of the objective lens up to the target track to beaccessed, and driving the actuator so as to shift the objective lens upto the target track on the basis of the calculated number of tracks.Therefore, it is possible to compensate a difference between the numberof tracks up to the target track and the number of tracks over which themotor advances the traverse, thereby enhancing the access precision.Further, it is possible to access the target track without obtaining theaddress where the objective lens is positioned in the middle of theaccess, thereby reducing the access time up to the target track.

Furthermore, according to claim 2 of the present invention, the opticaldisc device according to claim 1 further comprises a target numbercalculation means for calculating the number of tracks up to the targettrack on the basis of a current address where the objective lens iscurrently positioned, and the target track address; the motor drives thetraverse by a predetermined number of tracks as one step of unit traveldistance; the motor driving circuit calculates the number of steps fordriving the traverse by the motor, on the basis of the target number oftracks that is calculated by the target number calculation means, andthe unit travel distance of the motor, and drives the traverse by thecalculated number of steps; and the actuator driving means calculatesthe number of tracks from the position of the objective lens up to thetarget track after advancing the traverse by the motor, and drives theactuator at track intervals so as to shift the objective lens by thecalculated number of tracks. Therefore, it is possible to compensate adifference between the number of tracks up to the target track and thenumber of tracks over which the motor advances the traverse, therebyenhancing the access precision. Further, it is possible to access thetarget track without obtaining the address where the objective lens ispositioned in the middle of the access, thereby reducing the access timeup to the target track.

Furthermore, according to claim 3 of the present invention, the opticaldisc device as defined in claim 1 further comprises a target numbercalculation means for calculating the number of tracks up to the targettrack on the basis of a current address where the objective lens iscurrently positioned, and the target track address; the motor drives thetraverse by a predetermined number of tracks as one step of unit traveldistance; the motor driving circuit calculates the number of steps fordriving the traverse by the motor, on the basis of the target number oftracks that is calculated by the target number calculation means, andthe unit travel distance of the motor, and drives the traverse by thecalculated number of steps; and the actuator driving means calculatesthe distance from the position of the objective lens after advancing thetraverse by the motor, up to the target track, and drives the actuatorso as to shift the objective lens by the calculated distance. Therefore,it is possible to compensate a difference between the number of tracksup to the target track and the number of tracks over which the motoradvances the traverse, thereby enhancing the access precision. Further,it is possible to access the target track without obtaining the addresswhere the objective lens is positioned in the middle of the access,thereby reducing the access time up to the target track.

Furthermore, according to claim 4 of the present invention, an opticaldisc device comprises: an actuator for moving an objective lens thatirradiates an optical disc with a laser beam; a traverse for holding theobjective lens and the actuator so that the objective lens and theactuator are mutually movable; a motor for performing step driving toadvance the traverse for every unit travel distance; an actuator drivingmeans for generating a first tracking drive signal on the basis of anerror between the position of a track on the optical disc and theposition to which the objective lens applies the laser beam, andapplying the first tracking drive signal to the actuator to make theobjective lens follow the track on the optical disc; a ratio calculationmeans for shifting the objective lens at track intervals over apredetermined number of tracks to obtain the amount of shift of theobjective lens and the first tracking drive signal at this time, andcalculating the ratio of the amount of shift of the objective lens tothe first tracking drive signal; a target number calculation means forcalculating the number of tracks up to the target track on the basis ofa current address where the objective lens is currently positioned, anda target track address to be accessed; and a motor driving means forcalculating the number of steps for advancing the traverse by the motor,on the basis of the target number of tracks calculated by the targetnumber calculation means and the unit travel distance of the motor, anddriving the motor by the calculated number of steps; wherein theactuator driving means calculates the distance from the position of theobjective lens after advancing the traverse by the motor, up to thetarget track, generates a second tracking drive signal on the basis ofthe calculated distance and the ratio, and drives the actuator to shiftthe objective lens up to the target track. Therefore, the ratio betweenthe amount of shift of the objective lens, which is obtained whenshifting the objective lens at track intervals by a predetermined numberof tracks, and the first tracking drive signal obtained at this time canbe calculated in advance of performing access, whereby the secondtracking drive output can be accurately generated using the calculatedratio, on the basis of the distance from the position of the objectivelens after advancing the traverse by the motor to the target track, whenperforming access, resulting in enhanced access precision. Further, evenwhen the optical disc is replaced or the environment where the opticaldisc device is placed is changed, the second tracking drive output canbe calculated using the ratio adaptive to each optical disc or thecurrent environment, whereby the target track can be accessed with highaccuracy.

Furthermore, according to claim 5 of the present invention, in theoptical disc device according to claim 4, the ratio calculation meanscalculates the ratio of the amount of shift of the objective lens, whichamount of shift is obtained when rotating the optical disc with thetraverse being fixed and the objective lens following the track, to thefirst tracking drive signal. Therefore, the above-described ratio can becalculated in advance of performing access, whereby the second trackingdrive output can be accurately generated using the ratio, on the basisof the distance from the position of the objective lens after advancingthe traverse by the motor to the target track, when performing access,resulting in enhanced access precision. Further, even when the opticaldisc is replaced or the environment where the optical disc device isplaced is changed, the second tracking drive output can be calculatedusing the ratio adaptive to each optical disc or the currentenvironment, whereby the target track can be accessed with highaccuracy.

Furthermore, according to claim 6 of the present invention, in theoptical disc device according to claim 4, the ratio calculation meanscalculates the ratio of the amount of shift of the objective lens, whichamount of shift is obtained when advancing the traverse by apredetermined distance with the objective lens being held, to the firsttracking drive signal. Therefore, the above-described ratio can becalculated in advance of performing access, whereby the second trackingdrive output can be accurately generated using the ratio, on the basisof the distance from the position of the objective lens after advancingthe traverse by the motor to the target track, when performing access,resulting in enhanced access precision. Further, even when the opticaldisc is replaced or the environment where the optical disc device isplaced is changed, the second tracking drive output can be calculatedusing the ratio adaptive to each optical disc or the currentenvironment, whereby the target track can be accessed with highaccuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the construction of an opticaldisc device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating the positional relationships amongtracks on an optical disc, an objective lens, and a traverse duringtraverse seek, in the optical disc device according to the firstembodiment of the present invention.

FIG. 3 is a flowchart for explaining a method of performing traverseseek by the optical disc device according to the first embodiment of thepresent invention.

FIG. 4 is a block diagram illustrating the construction of an opticaldisc device according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating the positional relationships amongtracks on an optical disc, an objective lens, and a traverse duringtraverse seek, in the optical disc device according to the secondembodiment of the present invention.

FIG. 6 is a flowchart for explaining a method of performing traverseseek by the optical disc device according to the second embodiment ofthe present invention.

FIG. 7 is a block diagram illustrating the construction of an opticaldisc device according to a third embodiment of the present invention.

FIG. 8(a) is a flowchart for explaining a method of calculating theratio of an amount of shift of the objective lens to a tracking driveoutput by the optical disc device according to the third embodiment ofthe present invention, and FIG. 8(b) is a flowchart for explaining amethod of performing traverse seek.

FIG. 9 is a block diagram illustrating the construction of an opticaldisc device according to a fourth embodiment of the present invention.

FIG. 10(a) is a flowchart for explaining a method of calculating theratio of an amount of shift of the objective lens to a tracking driveoutput by the optical disc device according to the fourth embodiment ofthe present invention, and FIG. 10(b) is a flowchart for explaining amethod of performing traverse seek.

FIG. 11 is a block diagram illustrating the construction of an opticaldisc device according to a fifth embodiment of the present invention.

FIG. 12(a) is a flowchart for explaining a method of calculating theratio of an amount of shift of the objective lens to a tracking driveoutput by the optical disc device according to the fifth embodiment ofthe present invention, and FIG. 12(b) is a flowchart for explaining amethod of performing traverse seek.

FIG. 13 is a block diagram illustrating the construction of theconventional optical disc device.

FIG. 14 is a diagram illustrating the positional relationships amongtracks on an optical disc, an objective lens, and a traverse duringtraverse seek, in the conventional optical disc device.

FIG. 15 is a flowchart for explaining a method of performing traverseseek by the conventional optical disc device.

BEST MODE TO EXECUTE THE INVENTION

(Embodiment 1)

An optical disc device according to a first embodiment of the presentinvention will be described with reference to the drawings.

FIG. 1 is a block diagram illustrating the construction of an opticaldisc device 100 according to the first embodiment of the presentinvention.

The optical disc device 100 according to the first embodiment includes adisc motor 102 for rotating an optical disc 101 on which data arerecorded in tracks; an objective lens 103 for irradiating the opticaldisc 101 with a laser beam and receiving a reflected light beam; anactuator 104 for moving the objective lens 103 in the direction of theradius of the optical disc 101; a traverse 105 for holding the objectivelens 103 and the actuator 104 movably in the direction of the radius ofthe optical disc 101; and a motor 106 for driving the traverse 105 inthe direction of the radius of the optical disc 101. Further, theoptical disc device 100 includes a tracking error signal generationcircuit 107 for calculating an error between the position of a track onthe optical disc 101 and the position of the objective lens 103 (laserbeam irradiation position) on the basis of the reflected light beam thatis received by the objective lens 103, thereby generating a trackingerror signal as an error signal; a tracking servo filter 108 forgenerating a tracking drive output S108 for making the objective lens103 follow the track on the optical disc 101 (hereinafter referred to as“tracking-on”) on the basis of the tracking error signal outputted fromthe tracking error signal generation circuit 107; a target numbercalculation means 109 for calculating the number of tracks up to atarget track (hereinafter referred to as “target number of tracks”) onthe basis of a track address where the objective lens 103 is positionedat start of traverse seek (hereinafter referred to as “current trackaddress AD1”) and a target track address AD2 to be accessed; a stepnumber calculation means 110 for calculating the number of steps bywhich the traverse 105 should be shifted, on the basis of the targetnumber of tracks; a motor driving circuit 111 for driving the motor 106on the basis of the output of the step number calculation means 110; adifferential number calculation means 112 for calculating the number oftracks up to the target track from the track on which the objective lens103 is positioned (hereinafter referred to as “number of differentialtracks”) when driving the motor 106 by the calculated number of steps; atracking jump control means 113 for generating a control signal S113 onthe basis of the calculated number of differential tracks and applyingthe control signal S113 to an actuator driving circuit 114, therebydriving the actuator 104 at track intervals; and an actuator drivingcircuit 114 for driving the actuator 104 on the basis of the trackingdrive output S108 supplied from the tracking servo filter 108 or thecontrol signal S113 supplied from the tracking jump control means 113.

FIG. 2 shows the positional relationships among the tracks on theoptical disc 101, the objective lens 103, and the traverse 105 duringtraverse seek.

When a power is applied, the actuator 104 shifts the objective lens 103by a distance according to the power. When a pulse is applied, theactuator 104 shifts the objective lens 103 by the number of pulses thatare supplied at track interval D1, that is, makes the objective lens 103perform tracking jump.

When the pulse is applied, the motor 106 shifts the traverse 105 by thenumber of supplied pulses at predetermined interval L1 or integralmultiple mL1 of the predetermined interval L1. The predeterminedinterval L1 is equal to track interval D1 or integral multiple nD1 ofthe track interval D1. Hereinafter, the predetermined interval L1 or mL1that is a unit interval by which the motor 106 shifts the traverse 105is referred to as a step. Further, the motor 106 may be a stepping motorthat shifts the traverse 105 at step intervals.

The number of steps calculated by the step number calculation means 110is input to the motor driving circuit 111. Then, the motor drivingcircuit 111 outputs pulses as many as the number of steps to the motor106, thereby to drive the motor 106 by the number of steps.

The differential number calculation means 112 calculates the number ofdifferential tracks over which the objective lens 103 should be shifted,on the basis of the target number of tracks and the number of steps. Thenumber of differential tracks may be the remainder obtained whendividing the target number of tracks by the number of trackscorresponding to one step.

The actuator driving circuit 114 is supplied with either the trackingdrive output S108 indicating the amount of shift of the objective lens103 or the control signal S113 generated by the tracking jump controlmeans 113 on the basis of the number of differential tracks. When thetracking drive output S108 is input to the actuator driving circuit 114,the actuator driving circuit 114 outputs a power according to themagnitude of the tracking drive output S108 to the actuator 104, therebyto shift the objective lens 103. On the other hand, when the controlsignal S113 is input to the actuator driving circuit 114, the actuatordriving circuit 114 outputs pulses as many as the number of differentialtracks to the actuator 104, thereby making the objective lens 103perform tracking jump over tracks as many as the number of differentialtracks.

Next, a method of performing traverse seek in the optical disc device100 constructed as described above will be described with reference tothe drawings.

FIG. 3 is a flowchart for explaining the traverse seek method to beperformed by the optical disc device 100.

When traverse seek is started, an address acquisition means (not shown)obtains the current track address AD1 where the objective lens 103 ispositioned currently. Then, the target number calculation means 109calculates the target number of tracks on the basis of the target trackaddress AD2 and the current track address AD1. The step numbercalculation means 110 calculates the amount of shift of the traverse 105which is required for tracking on the target track, on the basis of thecalculated target number of tracks, and converts the calculated amountof shift into the number of steps of the motor 106. Further, thedifferential number calculation means 112 calculates the number ofdifferential tracks on the basis of the target number of tracks and thenumber of steps. As shown in FIG. 2, when the number of tracks from thetrack at which traverse seek is started up to the target track is 43 andthe predetermined interval L1 over which the motor 106 shifts thetraverse 105 by one step is equivalent to 13 tracks, the number of stepscalculated by the step number calculation means 110 is 3, and the numberof differential tracks calculated by the differential number calculationmeans 112 is 4 (step S11).

Next, the track-following operation is stopped, i.e., tracking-off iscarried out (step S12). Then, the motor driving circuit 111 drives themotor 106 by the number of steps calculated in step S11 to shift thetraverse 105. FIG. 2 shows the state where the traverse 105 is shiftedby 3 steps on the basis of the number of steps calculated by the stepnumber calculation means 110 (step S13). Then, tracking-on is carriedout again (step S14).

Since tracking jump can be carried out when the objective lens 103achieves tracking-on, the actuator driving circuit 114 drives theactuator 104 by the number of differential tracks on the basis of thecontrol signal S113 outputted from the tracking jump control means 113to shift the objective lens 103. FIG. 2 shows the state where theobjective lens 103 performs tracking jump by 4 tracks on the basis ofthe number of differential tracks calculated by the differential numbercalculation means 112 (step S15). Since, at this time, the objectivelens 103 is tracking on the target track, the address acquisition meansobtains the address of the track to complete the traverse seek (stepS16).

The optical disc device 100 according to the first embodiment isprovided with the step number calculation means 110 for calculating thenumber of steps of the motor 106 on the basis of the target number oftracks for traverse seek; the differential number calculation means 112for calculating the number of differential tracks over which theobjective lens 103 should be shifted, on the basis of the target numberof tracks and the number of steps; and the tracking jump control means113 for driving the actuator 104 at track intervals by supplying theactuator driving circuit 114 with the control signal S113 that isgenerated on the basis of the number of differential tracks; and themotor 106 is driven by the number of steps calculated by the step numbercalculation means 110 to shift the traverse 105, and thereafter,tracking jump is carried out by the number of differential tracks toshift the objective lens 103, whereby accurate access can be carried outby traverse seek.

Furthermore, the step of once obtaining the address after advancing thetraverse 105 and the step of calculating the number of tracks up to thetarget track address AD2, which steps are required for the conventionaloptical disc device 600, are dispensed with, resulting in a reduction inaccess time to the target track.

[Embodiment 2]

An optical disc device according to a second embodiment of the presentinvention will be described with reference to the drawings.

FIG. 4 is a block diagram illustrating the construction of an opticaldisc device 200 according to the second embodiment of the presentinvention. FIG. 5 is a diagram illustrating the positional relationshipsamong tracks on the optical disc 101, the objective lens 103, and thetraverse 105 during traverse seek. In FIG. 4, the same referencenumerals as those shown in FIG. 1 denote the same or correspondingparts.

In FIG. 4, reference numeral 201 denotes a tracking drive outputconversion means for calculating the amount of shift of the objectivelens 103 for accessing a target track, on the basis of the number ofdifferential tracks calculated by the differential number calculationmeans 112, and converting the calculated amount of shift into a trackingdrive output S201, and reference numeral 202 denotes an actuator drivingcircuit for driving the actuator 104 on the basis of a tracking driveoutput S108 outputted from the tracking servo filter 108 or a trackingdrive output S201 outputted from the tracking drive output conversionmeans 201.

The tracking drive output conversion means 201 controls shifting of theobjective lens 103 by the actuator 104 during traverse seek. That is,the tracking drive output conversion means 201 calculates the amount ofshift that is required for shifting the objective lens 103 by the numberof differential tracks, and outputs a tracking drive output S201 that isgenerated on the basis of the calculated value, to the actuator drivingcircuit 114.

The actuator driving circuit 202 receives either the tracking driveoutput S108 indicating the amount of shift of the objective lens 103 orthe tracking drive output S201 that is generated on the basis of thenumber of differential tracks by the tracking drive output conversionmeans 201. The actuator driving circuit 202 applies a voltage accordingto the magnitude of the tracking drive output S108 or S201 to theactuator 104, thereby to shift the objective lens 103.

Next, a description will be given of a method for performing traverseseek in the optical disc device 200 thus constructed with reference toFIG. 6.

FIG. 6 is a flowchart for explaining the traverse seek method by theoptical disc device 200.

When traverse seek is started and a current track address AD1 isobtained, the target number calculation means 109 calculates the targetnumber of tracks on the basis of the target track address AD2 and thecurrent track address AD1, and the step number calculation means 110calculates the number of steps of the motor required for tracking on thetarget track, on the basis of the calculated target number of tracks,and furthermore, the difference numeral calculation means 112 calculatesthe number of differential tracks on the basis of the target number oftracks and the number of steps (step S21). Then, the tracking driveoutput conversion means 201 calculates the amount of shift of theobjective lens on the basis of the number of differential tracks,generates a tracking drive output S201 on the basis of the calculatedvalue, and applies the tracking drive output S201 to the actuatordriving circuit 202 (step S22).

Thereafter, the track-following operation is stopped, i.e., tracking isturned off (step S23), and the motor driving circuit 111 drives themotor 106 by the number of steps calculated in step S21, therebyadvancing the traverse (step S24). Thereafter, the actuator drivingcircuit 202 drives the actuator 104 by the number of differential trackson the basis of the tracking drive output S201 from the tracking driveoutput conversion means 201, thereby shifting the lens (step S25).

In this way, tracking-on is carried out (step S26). At this time, sincethe objective lens 103 is tracking on the target track, the addressacquisition means obtains the address of the track to complete thetraverse seek (step S27).

In the optical disc device 200 according to the second embodiment, theamount of shift required for shifting the objective lens 103 by thenumber of differential tracks is calculated on the basis of the targetnumber of tracks for traverse seek and the number of steps of the motor106, and the tracking drive output S201 generated on the basis of thecalculated value is applied to the actuator driving circuit 202.Moreover, after advancing the traverse 105 by the motor 106, theactuator driving circuit 202 drives the actuator 104 on the basis of thetracking drive output S201 from the tracking drive output conversionmeans 201 to shift the objective lens 103, resulting in accurate accessby traverse seek.

(Embodiment 3)

An optical disc device according to a third embodiment of the presentinvention will be described with reference to the drawings.

FIG. 7 is a block diagram illustrating the construction of an opticaldisc device 300 according to a third embodiment of the presentinvention. In FIG. 7, the same reference numerals as those shown in FIG.4 denote the same or corresponding parts and, therefore, repeateddescription is not necessary.

In FIG. 7, 301 denotes a tracking servo filter that outputs a trackingdrive output S301 a and a lens shift amount S301 b indicating the amountof shift of the objective lens 103; 302 denotes a ratio calculationmeans for calculating the ratio between the amount of shift of theobjective lens 103 and the tracking drive output S301 a, and stores thecalculated ratio S302 b into a buffer 303.

Next, the operation of the optical disc device 300 constructed asdescribed above will be described with reference to the drawings.

FIG. 8(a) is a flowchart for explaining a method of calculating theratio between the amount of shift of the objective lens 103 and thetracking drive output S301 a, and FIG. 8(b) is a flowchart forexplaining a method of performing traverse seek.

In the optical disc device 300 according to the third embodiment, beforestarting traverse seek, that is, immediately after power-on orimmediately after loading of the optical disc 101, the ratio between theamount of shift of the objective lens 103 and the tracking drive outputS301 a is calculated. Initially, a method for calculating the ratiobetween the amount of shift of the objective lens 103 and the trackingdrive output S301 a will be described.

The ratio calculation means 302 outputs a tracking jump command S302 afor performing tracking jump over a predetermined number of tracks, tothe actuator driving circuit 202. Then, the actuator 104 is driven withthe traverse 105 being fixed, whereby tracking jump is carried out overthe predetermined number of tracks. At this time, the tracking errorsignal generation circuit 107 generates a tracking error signal that isan error signal between the position of the track on the optical discand the position to which the laser beam is applied by the objectivelens 103, and the tracking servo filter 301 outputs a lens shift amountS301 b indicating the amount of shift of the objective lens 103 and atracking drive output S301 a (step S31). Then, the ratio calculationmeans 302 calculates the ratio between the tracking drive output S301 aand the lens shift amount S301 b, which are output from the trackingservo filter 301 when performing tracking jump by the predeterminednumber of tracks (step S32). The buffer 303 holds the ratio S302 bsupplied from the ratio calculation means 302 (step S33).

After the ratio S302 b between the amount of shift of the objective lens103 and the tracking drive output S301 a is stored in the buffer 303,the optical disc device 300 goes into the state where traverse seek isexecutable.

Next, a method of performing traverse seek will be described.

When traverse seek is started, the target number calculation means 109calculates the target number of tracks for traverse seek on the basis ofthe target track address AD2 and the current track address AD1, the stepnumber calculation means 110 calculates the number of steps of the motor106 for tracking on the target track, on the basis of the calculatedtarget number of tracks, and the differential number calculation means112 calculates the number of differential tracks on the basis of thetarget number of tracks and the number of steps (step S41). Then, thetracking drive output conversion means 201 calculates the value byperforming the processes of steps S31 and S32 as described above, andgenerates a tracking drive output S201 using the ratio S302 b that isstored in the buffer 303 in step S33, and using the number ofdifferential tracks that is calculated by the differential numbercalculation means 112 (step S42).

Thereafter, the track-following operation is stopped, i.e., tracking isturned off (step S43), and the motor driving circuit 111 drives themotor 106 by the number of steps calculated in step S41, therebyadvancing the traverse (step S44). Thereafter, the actuator drivingcircuit 202 drives the actuator 104 on the basis of the tracking driveoutput S201 generated in step S42, thereby performing lens shift (stepS45).

Thereby, tracking-on is carried out (step S46). At this time, since theobjective lens 103 is tracking on the target track, the addressacquisition means obtains the address of the track to complete thetraverse seek processing (step S47).

In the optical disc device 300 according to the third embodiment, beforeperforming traverse seek, the ratio of the amount of shift of theobjective lens 103 (lens shift amount S301 b) that is obtained byperforming tracking jump over a predetermined number of tracks, to thetracking drive output S301 a at that time, is calculated, and the ratioS302 b as the calculated value is stored. Therefore, during traverseseek, the tracking drive output can be accurately generated from thenumber of differential tracks by using the stored ratio S302, wherebyaccess precision of traverse seek can be improved. Further, even whenthe optical disc 101 is replaced or the environment where the opticaldisc device is placed is changed, the tracking drive output can becalculated according to each optical disc or the current environment.

(Embodiment 4)

An optical disc device according to a fourth embodiment of the presentinvention will be described with reference to the drawings.

FIG. 9 is a block diagram illustrating the construction of an opticaldisc device 400 according to the fourth embodiment of the presentinvention. In FIG. 9, the same reference numerals as those shown in FIG.7 denote the same or corresponding parts, and therefore, repeateddescription is not necessary.

In FIG. 9, 401 denotes a ratio calculation means for calculating theratio between the tracking drive output S301 a and the objective lens103 on the basis of an rpm S102 indicating the number of revolutions ofthe disc motor 102, the tracking drive output S301 a outputted from thetracking servo filter 301, and the lens shift amount S301 b, and thenstoring the calculated ratio S401 into the buffer 303.

Next, the operation of the optical disc device 400 constituted asdescribed above will be described with reference to the drawings.

FIG. 10(a) is a flowchart for explaining a method of calculating theratio between the amount of shift of the objective lens 103 and thetracking drive output S301 a by the optical disc device 400, and FIG.10(b) is a flowchart for explaining the method of performing traverseseek.

The optical disc device 400 according to the fourth embodimentcalculates the ratio between the amount of shift of the objective lens103 and the tracking drive output S301 a, before starting traverse seek,that is, immediately after power-on or immediately after loading of theoptical disc 101. Initially, the method of calculating the ratio betweenthe amount of shift of the objective lens 103 and the tracking driveoutput S301 a will be described.

First of all, in the optical disc device 400, tracing is carried out fora predetermined period of time. That is, the disc motor 102 is rotatedunder the state where the objective lens 103 is tracking on and thetraverse 105 is fixed. When the optical disc 101 is rotated under thetracking-on state, the objective lens 103 shifts by one track whiletracing the track on the optical disc 101, and therefore, the trackingservo filter 301 outputs a tracking drive output S301 a for shifting theobjective lens 103 by one track, and a lens shift amount S301 bindicating the amount of shift of the objective lens 103 for one track.Accordingly, the ratio calculation means 401 obtains, from the rpm 102,the number of tracks traced by the objective lens 103, and also objectsthe tracking drive output S301 a which is outputted from the trackingservo filter 301 when the number of tracks are traced, and the lensshift amount S301 b (step S51).

Next, the ratio calculation means 401 calculates the ratio between thetracking drive output S301 a and the lens shift amount S301 b, which areoutput from the tracking servo filter 301 when the objective lens 103traces tracks by the number of tracks obtained from the rpm S102 (stepS52). Then, the buffer 303 holds the ratio S401 from the ratiocalculation means 401 (step S53).

After storing the ratio S401 of the tracking drive output to the amountof shift of the objective lens 103 into the buffer 303, the optical discdevice 400 goes into the state where it can execute traverse seek.

Next, the method of performing traverse seek will be described.

When traverse seek is started, the target number calculation means 109calculates the target number of tracks for traverse seek on the basis ofthe target track address AD2 and the current track address AD1, and thestep number calculation means 110 calculates the number of steps of themotor 106 required for tracking on the target track, and thedifferential number calculation means 112 calculates the number ofdifferential tracks on the basis of the target number of tracks and thenumber of steps (step S61). Then, the tracking drive output conversionmeans 201 calculates the value by performing the processes of steps S51and S52, and generates a tracking drive output S201 by using the ratioS401. stored in the buffer 303 in step S53, and the number ofdifferential tracks calculated by the differential number calculationmeans 112 (step S62).

Thereafter, the track-following operation is stopped, i.e., tracking-offis carried out (step S63), and the motor driving circuit 111 drives themotor 106 by the number of steps calculated in step S61, therebyadvancing the traverse (step S64). Thereafter, the actuator drivingcircuit 202 drives the actuator 104 on the basis of the tracking driveoutput S201 generated in step S62, thereby performing lens shift (stepS65).

Thereby, tracking-on is carried out (step S66). Since, at this time, theobjective lens 103 is tracking on the target track, the addressacquisition means obtains the address of the track to complete thetraverse seek processing (step S67).

In the optical disc device 400 according to the fourth embodiment,before performing traverse seek, the ratio between the amount of shiftof the objective lens 103 (lens shift amount S301 b) which is obtainedby rotating the disc motor 102, and the tracking drive output S301 a,under the state where the objective lens 103 is tracking on and thetraverse 105 is fixed, and the calculated ratio S401 is stored in thebuffer 303. Therefore, when performing traverse seek, the tracking driveoutput S201 can be accurately generated from the number of differentialtracks by using the stored ratio S401, whereby access precision oftraverse seek can be improved. Further, even when the optical disc 101is replaced or the environment where the optical disc device is placedis changed, a tracking drive output S201 adaptive to each optical discor current environment can be generated.

(Embodiment 5)

An optical disc device according to a fifth embodiment of the presentinvention will be described with reference to the drawings.

FIG. 11 is a block diagram illustrating the construction of an opticaldisc device 500 according to the fifth embodiment of the presentinvention. In FIG. 11, the same reference numerals as those shown inFIG. 9 denote the same or corresponding parts and, therefore, repeateddescription is not necessary.

In FIG. 11, 501 denotes a ratio calculation means for calculating theratio between the tracking drive output S301 a and the lens shift amountS301 b, which are obtained when advancing the traverse for apredetermined distance by the motor 106 under the state where theobjective lens 103 is held by fixing the actuator 104, and storing thecalculated ratio S501 in the buffer 303.

Next, the operation of the optical disc device 500 thus constructed willbe described with reference to the drawings.

FIG. 12(a) is a flowchart for explaining the method of calculating theratio between the amount of shift of the objective lens 103 and thetracking drive output S301 a, and FIG. 12(b) is a flowchart forexplaining the method of performing traverse seek.

The optical disc device 500 according to the fifth embodiment calculatesthe ratio between the amount of shift of the objective lens 103 and thetracking drive output S301 a, before starting traverse seek, that is,immediately after power-on or immediately after loading of the opticaldisc 101. Initially, the method of calculating the ratio between theamount of shift of the objective lens 103 and the tracking drive outputS301 a will be described.

When the ratio calculation means 501 outputs a hold track command S501 afor holding the objective lens 103 to the actuator driving circuit 202,the actuator driving circuit 202 fixes the actuator 104 to hold theobjective lens 103 (step S71). Next, the ratio calculation means 501outputs a traverse advance command S501 b for advancing the traverse 105by a predetermined distance, to the motor 106, and the motor 106advances the traverse 105 according to the command S501 b. At this time,the tracking servo filter 301 outputs a lens shift amount S301 b and atracking drive output S301 a on the basis of a tracking error signalgenerated by the tracking error signal generation circuit 107 (stepS72). Then, the ratio calculation means 501 calculates the ratio betweenthe tracking drive output S301 a and the lens shift amount S301 b, whichare output from the tracking servo filter 301 when advancing thetraverse 105 by a predetermined distance with the objective lens 103being held (step S73). Then, the buffer 303 holds the ratio S501 csupplied from the ratio calculation means 501 (step S74).

After the ratio S501 c of the tracking drive output to the amount ofshift of the objective lens 103 is stored in the buffer 303 in this way,the optical disc device 500 goes into the state where traverse seek isexecutable.

Next, the method of performing traverse seek will be described.

When traverse seek is started, the target number calculation means 109calculates the target number of tracks on the basis of the target trackaddress AD2 and the current track address AD1, and the step numbercalculation means 110 calculates the number of steps of the motor 106for tracking on the target track, and the differential numbercalculation means 112 calculates the number of differential tracks onthe basis of the target number of tracks and the number of steps (stepS81). Then, as described above, the tracking drive output conversionmeans 201 calculates the value by performing the processes of steps S71to S73, and generates a tracking drive output S201 on the basis of theratio S501 c stored in the buffer 303 in step S74, and the number ofdifferential tracks calculated by the differential number calculationmeans 112 (step S82).

Thereafter, the track-following operation is stopped, i.e., tracking-offis carried out (step S83), and the motor drive circuit 111 drives themotor 106 by the number of steps calculated in step S81, therebyadvancing the traverse (step S84). Thereafter, the actuator drivingcircuit 202 drives the actuator 104 on the basis of the tracking driveoutput S201 generated in step S82, thereby performing lens shift (stepS85).

Thereby, tracking-on is carried out (step S86). Since, at this time, theobjective lens 103 is tracking on the target track, the addressacquisition obtains the address of the track to complete traverse seekprocessing (step S87).

In the optical disc device 500 according to the fifth embodiment, beforeperforming traverse seek, the ratio of the amount of shift of theobjective lens 103 (lens shift amount S301 b) that is obtained byadvancing the traverse 105 by a predetermined distance with theobjective lens 103 being held, to the tracking drive output S301 a atthis time, and the calculated ratio S501 c is stored. Therefore, whenperforming traverse seek, the tracking drive output S201 can beaccurately generated from the number of differential tracks by using thestored ratio S501 c, whereby access precision of traverse seek can beimproved. Further, even when the optical disc 101 is replaced or theenvironment where the optical disc device is placed is changed, atracking drive output S201 adaptive to each optical disc or currentenvironment can be generated.

Applicability in Industry

An optical disc device according to the present invention calculates anamount of shift of a traverse and an amount of shift of an objectivelens after shifting the traverse, and drives the traverse and theobjective lens on the basis of the calculated values. Therefore, evenwhen performing traverse seek by advancing the traverse at intervals ofplural tracks, access to a target track can be made with accuracy in ashort time.

1. An optical disc device comprising: an actuator for moving anobjective lens that irradiates an optical disc with a laser beam; atraverse for holding the objective lens and the actuator so that theobjective lens and the actuator are mutually movable; a motor forperforming step driving to advance the traverse for every unit traveldistance; an actuator driving means for driving the actuator on thebasis of an error between the position of a track on the optical discand the position to which the objective lens applies the laser beam,thereby to make the objective lens follow the track on the optical disc;and a motor driving means for calculating the number of steps on thebasis of the number of tracks from the position of the objective lens upto a target track to be accessed, and driving the traverse by thecalculated number of steps; wherein said actuator driving meanscalculates the number of tracks from the position of the objective lensup to the target track to be accessed, and driving the actuator so as toshift the objective lens up to the target track on the basis of thecalculated number of tracks.
 2. An optical disc device as defined inclaim 1 further comprising: a target number calculation means forcalculating the number of tracks up to the target track on the basis ofa current address where the objective lens is currently positioned, andthe target track address; wherein said motor drives the traverse by apredetermined number of tracks as one step of unit travel distance; saidmotor driving circuit calculates the number of steps for driving thetraverse by the motor, on the basis of the target number of tracks thatis calculated by the target number calculation means, and the unittravel distance of the motor, and drives the traverse by the calculatednumber of steps; and said actuator driving means calculates the numberof tracks from the position of the objective lens up to the target trackafter advancing the traverse by the motor, and drives the actuator attrack intervals so as to shift the objective lens by the calculatednumber of tracks.
 3. An optical disc device as defined in claim 1further comprising: a target number calculation means for calculatingthe number of tracks up to the target track on the basis of a currentaddress where the objective lens is currently positioned, and the targettrack address; wherein said motor drives the traverse by a predeterminednumber of tracks as one step of unit travel distance; said motor drivingcircuit calculates the number of steps for driving the traverse by themotor, on the basis of the target number of tracks that is calculated bythe target number calculation means, and the unit travel distance of themotor, and drives the traverse by the calculated number of steps; andsaid actuator driving means calculates the distance from the position ofthe objective lens after advancing the traverse by the motor, up to thetarget track, and drives the actuator so as to shift the objective lensby the calculated distance.
 4. An optical disc device comprising: anactuator for moving an objective lens that irradiates an optical discwith a laser beam; a traverse for holding the objective lens and theactuator so that the objective lens and the actuator are mutuallymovable; a motor for performing step driving to advance the traverse forevery unit travel distance; an actuator driving means for generating afirst tracking drive signal on the basis of an error between theposition of a track on the optical disc and the position to which theobjective lens applies the laser beam, and applying the first trackingdrive signal to the actuator to make the objective lens follow the trackon the optical disc; a ratio calculation means for shifting theobjective lens at track intervals over a predetermined number of tracksto obtain the amount of shift of the objective lens and the firsttracking drive signal at this time, and calculating the ratio of theamount of shift of the objective lens to the first tracking drivesignal; a target number calculation means for calculating the number oftracks up to the target track on the basis of a current address wherethe objective lens is currently positioned, and a target track addressto be accessed; and a motor driving means for calculating the number ofsteps for advancing the traverse by the motor, on the basis of thetarget number of tracks calculated by the target number calculationmeans and the unit travel distance of the motor, and driving the motorby the calculated number of steps; wherein said actuator driving meanscalculates the distance from the position of the objective lens afteradvancing the traverse by the motor, up to the target track, generates asecond tracking drive signal on the basis of the calculated distance andthe ratio, and drives the actuator to shift the objective lens up to thetarget track.
 5. An optical disc device as defined in claim 4 whereinsaid ratio calculation means calculates the ratio of the amount of shiftof the objective lens, which amount of shift is obtained when rotatingthe optical disc with the traverse being fixed and the objective lensfollowing the track, to the first tracking drive signal.
 6. An opticaldisc device as defined in claim 4 wherein said ratio calculation meanscalculates the ratio of the amount of shift of the objective lens, whichamount of shift is obtained when advancing the traverse by apredetermined distance with the objective lens being held, to the firsttracking drive signal.